Fluid regulators, such as gas pressure regulators are in common use in gas pipeline systems to assist in maintaining system pressure within acceptable limits. As an example, the primary function of a gas pressure regulator is to match the flow of gas through the regulator to the demand for gas placed upon the system. Also, the pressure regulator must maintain the system pressure within acceptable limits. In one type of such gas pressure regulator, a diaphragm assembly is set to a predetermined set point by an adjustable control spring. A pivoting lever is connected to the diaphragm assembly and responds to diaphragm pressure to throttle a disk with respect to an orifice, where the orifice communicates the inlet pressure to the regulator outlet.
The disk and orifice may be referred to as portions of a restricting element which are placed into the gas flow stream and provide a variable restriction that can modulate the flow of gas through the regulator in accordance with the sensed downstream pressure. The diaphragm assembly may also be called a loading element which can provide a loading force to the restricting element. Thus, a loading pressure is applied to the diaphragm in response to the sensed downstream pressure to produce a loading force that will act to close the restricting element. The diaphragm spring provides a reverse loading force which acts to open the restricting element.
Accordingly, if the load flow in the pipeline system decreases, then the regulator flow also must decrease in order to avoid having the regulator place too much gas into the system which would tend to increase the downstream pipeline pressure. On the other hand, if the load flow increases, then the regulator flow also must increase in order to keep the pipeline pressure at the regulator output from decreasing due to a shortage of gas in the pipeline system.
Occasionally, a certain amount of operational instability in the performance of currently used fluid pressure regulators has been noted. In particular, one noted instability involves a fast cycling instability in regulator operation with a repetition frequency of 20-50 hertz. This type of regulator instability has been solved during the design and development of prior pressure reducing regulators by providing a stabilizing flapper in the throat of the regulator lower actuator casing. It is believed that the stabilizing flapper acted in the manner of an air shock to dampen the regulator operational instability.
In this prior regulator, known as the Fisher Type 627R Regulator, a plastic frame was sized to be inserted into the throat and a rubber flapper was mounted therein so as to extend across and block off the throat. A single hole was located in the outer perimeter of the plastic frame and in a position so as not to be covered by the rubber flapper. This single hole in the plastic frame supporting the flapper was to provide sensing of the downstream pressure and so as to communicate this downstream pressure through the throat and into the regulator diaphragm casing. Also, during overpressure conditions, the rubber flapper may be flexed so that the stabilizer opens up fully to unblock the throat and to allow the flow of fluid from the pipeline into the throat and through the diaphragm casing and eventually into the upper casing so as to exit from the regulator venting port during internal relief of the unit.
One difficulty noticed with the single hole stabilizer developed for this prior regulator is that downstream pressure sensing varies in accordance with the location and orientation of the hole. That is, the best downstream pressure sensing is achieved when the single hole location and orientation is as close as possible to the downstream area and the least amount of downstream pressure sensing is noted when the single hole is located and oriented away from the downstream area and is placed towards the upstream area. Thus, the regulator capacity is a function of the location and orientation of the single hole in the stabilizer unit.
It is desired to provide a stabilizer for pressure reducing regulators which decreases regulator instability and which is not affected by the location and orientation of the stabilizer mounting within the regulator throat. Further, it is desired to provide a stabilizer for use as a retrofit cartridge to be mounted into existing fluid pressure regulators so that the stabilizing cartridge can become a permanent component of the regulator and not become loose or otherwise dislodged during the life of the regulator.